1. Field of the Invention
The present invention pertains to liquid homogeneous substantially unbuilt enzyme containing detergent compositions.
2. Description of the Art
To be satisfactory for washing or pre-treating and subsequent washing of heavily soiled fabrics, such as cotton and synthetic fabrics, liquid detergent compositions contain an adequate concentration of detergent compounds. In addition, they must remain stable and homogeneous when subjected to various storage conditions and be designed for use in both horizontal (tumble drum type) and upright (vertical agitator type) washing machines and for topical application as well as for handwashing.
Liquid, heavy duty detergent compositions a synthetic organic detergent compound, which is generally anionic, nonionic or mixed anionic-nonionic in nature; an inorganic builder salt; and a solvent, are disclosed, for example, in U.S. Pat. Nos. 2,551,634; 2,908,651; 2,920,045; 2,947,702; 3,239,468; 3,272,753; 3,393,154; 3,554,916; 3,697,451; 3,709,838; Belgian patents 613,165; 665,532; 794,713 and 817,267; British Pat. No. 759,877; 842,813; and German application Nos. 1,617,119; 1,937,682; 2,327,861; 2,330,840; 2,361,448 and 2,362,114. These compositions frequently contain a hydrotrope or solubilizing agent to permit the addition of sufficient quantities of surfactants and usual builder salts to provide a reasonable volume usage/performance ratio. Others are substantially anhydrous liquid compositions containing an alkanolamine component (U.S. Pat. No. 3,528,925). Still others contain a soap component (U.S. Pat. Nos. 2,875,153 and 2,543,744).
It is well-known that the formulation of enzyme containing liquid detergent compositions is a very delicate task due to the rapid decrease of the enzymatic activity in aqueous medium during storage. In fact, the difficulties flowing from the inherent losses in enzymatic activity are such that until now, this problem could not be solved satisfactorily. The significance of these obstacles will even be better understood when considering that the desirability for formulating liquid detergent compositions containing enzymes is known for a good time already. The absence of any practical solution to this highly unsatisfactory enzymatic activity retention in aqueous detergent medium confirms all the more, both, the instability of enzymes in current liquid detergents compositions and concomitantly the difficulties for selectively formulating a liquid composition containing enzymes which might be of commercial interest.
The state of the art is scattered in respect to this particular aspect of detergent technology. So, for example, it is known from Dutch patent application No. 66.08106 that proteolytic enzymes do only have a limited stability in aqueous medium. In addition to this, it is expressed that most detergent ingredients such as phosphates, carbonates, and sulfates have an adverse effect on the activity of these enzymes as well as on their stability in detergent solution. This reference amounts to an explanation why (proteolytic) enzymes are until now only incorporated into granular detergent compositions. No concrete solution however is suggested in the art relative to the deficient stability.
From the discosures of "BIOCHEMICA ET BIOPHYSICA ACTA," Vol. 6 (1950), pages 237 et seq., is known that sequestering agents in general exert a destabilizing effect on proteolytic enzymes in aqueous medium. Citric acid, oxalic acid, ethylenediaminetetracetic acid, and nitrilotrilotriacetic acid examplify this known destabilizing effect. German patent application DOS No. 2,301,728 is representative of the known prior art. It discloses that various enzyme preparations can be incorporated into liquid detergent compositions preferably in conjunction with detergent sequestering builders.
As can be seen from the foregoing, a substantial effort has been expanded in developing built and builder-free detergent compositions in liquid form. Yet, there are several problems associated with the art-disclosed compositions which render them less optimal for wide scale use, undesirable from an ecological standpoint in improperly treated sewage, objectionable from a performance point of view in cleaning both natural and synthetic fibers and subject to deactivation of the enzyme component during storage.
It has now been found that these known deficiencies can be avoided by formulating enzyme containing liquid detergent compositions' comprising a minor amount of a specific polyacid and a certain level of free calcium ions.
It has also been found that liquid, concentrated, heavy duty detergent compositions containing a major amount of a mixture of a polyethoxylated nonionic and a synthetic anionic surfactant in conjunction with a polyacid, a protease and the free calcium ions and having a pH in the range of from 6.0 to 7.5, exhibit superior removal of bleach-sensitive stains by topical application and through-the-wash fabric cleaning.
These liquid, concentrated, heavy duty detergent compositions exhibit good physical properties, remain hoogeneous and stable under severe storage conditions and stand the addition of many usual adjuvants.
It is an object of this invention to provide liquid, concentrated, homogeneous, stable enzyme containing heavy duty detergent compositions which exhibit excellent cleaning and superior bleach-sensitive stain removal by topical application and through-the-wash fabric cleaning.
It is another object herein to provide liquid, concentrated, homogeneous, stable, heavy duty detergent compositions which retain an effective enzyme activity under prolonged storage conditions.
It is still another object herein to provide liquid, concentrated, homogeneous, stable, enzyme containing heavy duty detergent compositions acceptable from an ecological standpoint.
These and other objects can now be met as will be seen from the following disclosure.